U.S. patent number 8,842,867 [Application Number 12/379,368] was granted by the patent office on 2014-09-23 for loudspeaker box with a variable radiation characteristic.
This patent grant is currently assigned to D & B Audiotechnik AG. The grantee listed for this patent is Frank Bothe. Invention is credited to Frank Bothe.
United States Patent |
8,842,867 |
Bothe |
September 23, 2014 |
Loudspeaker box with a variable radiation characteristic
Abstract
A loudspeaker box (300) has a loudspeaker housing (1) and a
sound source (3a) with a non-rotationally symmetrical radiation
characteristic. The sound path of the sound source (3a) contains an
acoustic element (4) which dilates or constricts the radiation of
sound in at least one radiation plane. The loudspeaker box (300)
comprises a mechanism which can be used to position the sound
source (3a) and the acoustic element (4) in different rotational
positions relative to one another.
Inventors: |
Bothe; Frank (Backnang,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bothe; Frank |
Backnang |
N/A |
DE |
|
|
Assignee: |
D & B Audiotechnik AG
(Backnang, DE)
|
Family
ID: |
40469011 |
Appl.
No.: |
12/379,368 |
Filed: |
February 19, 2009 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090214067 A1 |
Aug 27, 2009 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 22, 2008 [DE] |
|
|
10 2008 010 524 |
|
Current U.S.
Class: |
381/345; 381/337;
381/387; 381/339 |
Current CPC
Class: |
H04R
1/345 (20130101); H04R 1/403 (20130101); H04R
2201/401 (20130101); H04R 1/26 (20130101); H04R
1/026 (20130101); H04R 27/00 (20130101) |
Current International
Class: |
H04R
1/20 (20060101); H04R 1/02 (20060101) |
Field of
Search: |
;381/339,345,337,387 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
21267 |
|
Mar 1956 |
|
DE |
|
297 17 524 |
|
Feb 1998 |
|
DE |
|
102 30 409 |
|
Jul 2002 |
|
DE |
|
102 30 409 |
|
Oct 2003 |
|
DE |
|
10 2005 022 869 |
|
Nov 2006 |
|
DE |
|
1 635 606 |
|
Mar 2006 |
|
EP |
|
2 425 436 |
|
Oct 2006 |
|
GB |
|
2004-64507 |
|
Feb 2004 |
|
JP |
|
Other References
Englsih translation DE 10230409. cited by examiner .
Model 2395, JBL Catalogue, website action audio, pp. 14. cited by
applicant .
http://wwwalconsaudio.com/site/index.html, p. 1. cited by applicant
.
British Search Report dated May 14, 2009 and issued in
corresponding British Patent Application GB0901153.7. cited by
applicant.
|
Primary Examiner: Enad; Elvin G
Assistant Examiner: Hinson; Ronald
Claims
The invention claimed is:
1. A loudspeaker box comprising: a loudspeaker housing; a sound
source with a non-rotationally symmetrical radiation
characteristic; an acoustic element which is arranged in the sound
path of the sound source and which dilates the radiation of sound
in a first radiation plane and leaves the radiation of sound
essentially unchanged in a second radiation plane that is rotated
by 90 degrees with respect to the first radiation plane; and a
mechanism configured to position the sound source and the acoustic
element in different rotational positions relative to one
another.
2. A loudspeaker box according to claim 1, wherein the acoustic
element comprises one or more perforated panels.
3. A loudspeaker box according to claim 1, wherein the acoustic
element comprises a set of parallel lamellae.
4. A loudspeaker box according to claim 1, wherein the acoustic
element comprises a porous material.
5. A loudspeaker box according to claim 1, wherein the acoustic
element is a transmissive body.
6. A loudspeaker box according to claim 1, wherein the mechanism is
in a form such that the sound source can be repositioned in
reference to the loudspeaker housing.
7. A loudspeaker box according to claim 1, wherein the mechanism is
in a form such that the acoustic element can be repositioned in
reference to the loudspeaker housing.
8. A loudspeaker box according to claim 1, wherein the sound source
is quasi-linear.
9. A loudspeaker box according to claim 8, wherein the sound source
comprises a diffraction gap associated with a loudspeaker.
10. A loudspeaker box according to claim 1, wherein the sound
source comprises a ribbon loudspeaker.
11. A loudspeaker box according to claim 8, wherein the sound
source comprises an air motion transformer.
12. A loudspeaker box according to claim 8, wherein the sound
source comprises a linear arrangement comprising a plurality of
loudspeakers.
13. A loudspeaker box according to claim 8, wherein the sound
source has a radiation characteristic of no more than 25.degree. in
the plane defined by the quasi-linear profile of the sound
source.
14. A loudspeaker box according to claim 8, wherein the acoustic
element dilates the radiation in a plane defined by the
quasi-linear profile of the sound source to at least 30.degree.
when positioned such that the first radiation plane coincides with
the plane defined by the quasi-linear profile of the sound
source.
15. A loudspeaker box according to claim 8, wherein the acoustic
element leaves the radiation in a plane defined by the quasi-linear
profile of the sound source essentially unchanged when positioned
such that the second radiation plane coincides with the plane
defined by the quasi-linear profile of the sound source.
16. A loudspeaker box according to claim 8, wherein the
quasi-linear sound source has a radiation characteristic of at
least 60.degree. in the plane oriented at right angles to the
quasi-linear profile of the sound source.
17. A loudspeaker box according to claim 16, wherein the acoustic
element leaves the radiation in a plane oriented at right angles to
the quasi-linear profile of the sound source essentially unchanged
when positioned such that the first radiation plane coincides with
the plane defined by the quasi-linear profile of the sound
source.
18. A loudspeaker box according to claim 16, wherein the acoustic
element dilates the radiation in a plane oriented at right angles
to the quasi-linear profile of the sound source to at least
80.degree. when positioned such that the second radiation plane
coincides with the plane defined by the quasi-linear profile of the
sound source.
19. A loudspeaker box according to claim 1, wherein the loudspeaker
housing has a conical cross section.
20. A loudspeaker box comprising: a loudspeaker housing; a sound
source with a non-rotationally symmetrical radiation
characteristic; a positioning mechanism to position at least one
acoustic element, which dilates the radiation of sound in a first
radiation plane and leaves the radiation of sound essentially
unchanged in a second radiation plane that is rotated by 90 degrees
with respect to the first radiation plane, into the sound path of
the sound source, the positioning mechanism being configured to
position the acoustic element in the sound path of the sound source
in one situation of use and to remove the acoustic element from the
sound path of the sound source in another situation of use; and a
rotating mechanism configured to rotate the sound source in
different rotational positions relative to the loudspeaker
housing.
21. A loudspeaker box according to claim 20, wherein the
positioning mechanism is a coupling.
22. A loudspeaker box according to claim 20, wherein the
positioning mechanism is a swivel, hinged or sliding mechanism
which can be used to move the acoustic element either into or out
of the sound path of the sound source.
23. A loudspeaker box according to claim 20, wherein the sound
source has a quasi-linear profile.
24. A loudspeaker box according to claim 21, wherein the sound
source has a radiation characteristic of no more than 25.degree. in
the plane defined by the quasi-linear profile of the sound
source.
25. A loudspeaker box according to claim 24, wherein as soon as the
acoustic element is in the sound path of the quasi-linear sound
source , the acoustic element dilates the radiation characteristic
in the plane defined by the quasi-linear profile of the sound
source to at least 30.degree..
26. A system comprising a plurality of loudspeaker boxes according
to claim 1.
27. A system according to claim 26, wherein the arrangement is a
line array.
28. A loudspeaker box according to claim 20, wherein, by operating
both the positioning mechanism and the rotating mechanism, the
angular radiation characteristic relative to the loudspeaker
housing is changed between a characteristic adapted for an upright
use of the loudspeaker housing and a characteristic adapted for a
use on a side of the loudspeaker housing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of German Application No.
10-2008 010 524.4, filed with the German Intellectual Property
Office on Feb. 22, 2008, the disclosure of which is incorporated
herein by reference.
FIELD
The invention relates to a loudspeaker box and to arrangements
comprising a plurality of loudspeaker boxes.
BACKGROUND
Loudspeaker systems typically have different radiation properties
in the horizontal and vertical planes. This is generally used in a
targeted fashion to provide even sound for audience areas of
various geometry. A customary measure for obtaining a defined
radiation behaviour for a sound source is to use particular
loudspeaker types or a horn for the sound routing.
Loudspeaker boxes can be operated as individual systems or in
loudspeaker groups. Typical individual systems are loudspeaker
boxes which have been set up in the domestic sector, for example.
Loudspeaker groups are frequently used when sound needs to be
provided for larger areas or spaces. By way of example, loudspeaker
groups are used for concerts, e.g. for open-air concerts or in
halls. In the case of loudspeaker groups, it is necessary to take
account not only of the acoustic properties of the individual
loudspeaker boxes but also of the arrangement of the loudspeaker
boxes relative to one another, which significantly influences the
overall radiation behaviour of the loudspeaker group. One
frequently used loudspeaker group is what are known as line arrays,
for example, in which loudspeaker boxes are arranged beneath one
another in a vertical column.
SUMMARY
The invention is based on the object of providing loudspeaker boxes
which can be used in versatile fashion.
The object on which the invention is based is achieved by the
features of the independent claims. Advantageous embodiments and
developments of the invention are specified in the dependent
claims.
According to claim 1, the loudspeaker box has a loudspeaker housing
and a sound source with a non-rotationally symmetrical radiation
characteristic. The sound path of the sound source contains an
acoustic element which dilates or constricts the radiation of sound
in at least one radiation plane. In addition, the loudspeaker box
comprises a mechanism which can be used to position the sound
source and the acoustic element in different rotational positions
relative to one another.
The acoustic element brings about a change in the acoustic
wavefront, and repositioning the sound source relative to the
acoustic element changes the radiation angle of the wavefront
emitted by the loudspeaker box in at least one plane in reference
to the sound source. The effect which can be achieved by this is
that the loudspeaker box is suitable both for operation in a
horizontal position and for operation in a vertical position. This
allows the loudspeaker box to be configured for different
applications or fields of use. By way of example, it can be used as
an individual loudspeaker box or in an array arrangement comprising
a plurality of loudspeaker boxes (e.g. line array comprising a
column of horizontally oriented loudspeaker boxes).
In line with one expedient refinement, the acoustic element dilates
the sound field. In this case, the radiation of sound is dilated in
the at least one radiation plane. However, it is also possible for
the acoustic element to constrict the sound field in at least one
radiation plane. In many cases, functionally comparable solutions
in reference to the radiation characteristic can be provided by
acoustic elements which constrict the sound field or dilate the
sound field.
The acoustic element can be implemented in a wide variety of ways.
One option is for the acoustic element to comprise one or more
perforated panels. The perforated panels alter the phase response
or the propagation-time response of the acoustic wave when passing
through the holes such that the wavefront curves outwards, i.e. is
dilated.
In line with another implementation option, the acoustic element
may comprise a set of parallel lamellae. Inclination of the
lamellae with respect to the acoustic axis means that they act as
detour elements which delay the sound and thereby alter the
wavefront. The length of the lamellae in the path of the sound
allows the propagation delay and hence the deformation of the
wavefront to be set in a targeted fashion. Instead of a set of
lamellae, it is also possible to integrate other detour elements
with comparable effect into the sound path.
Another way for the wavefront to be influenced by the acoustic
element is to provide an acoustic element comprising a porous
material.
Said and other acoustic elements can be operated in transmission
and are therefore also frequently referred to as "acoustic lenses".
However, it is also possible for the acoustic element to be
designed in the form of a reflective body. A reflective body of
this kind may be arranged as a repositionable or rotatable core
within or partially within a horn, for example, and can influence
the radiation characteristic of the horn and alter it when
repositioned relative to the horn.
Many and diverse combinations of the aforementioned forms of an
acoustic element are possible. All of said implementations of an
acoustic element operated in transmission can be combined. In
addition, the acoustic element may also be a combination of
transmissive bodies and reflective bodies.
The mechanism for repositioning the acoustic element relative to
the sound source may be in a form such that the sound source can be
repositioned (e.g. rotated) in reference to the loudspeaker
housing. In this case, the acoustic element may be fitted on the
loudspeaker housing at a fixed location, for example.
Another option is to design the mechanism such that the acoustic
element can be repositioned in reference to the loudspeaker
housing. In this case, a sound source which cannot be rotated
relative to the loudspeaker-housing may be used, for example.
The sound source may have a linear or quasi-linear profile and be
implemented by the diffraction gap of a horn (what is known as a
diffraction horn), for example. Such a horn typically has a smaller
radiation angle in the plane defined by the profile of the
diffraction gap than in the plane which is at right angles thereto.
However, it is also possible to implement a sound source having a
linear profile in another way, e.g. by using a quasi-linear sound
generator such as a ribbon loudspeaker, an air motion transformer
(AMT) or a linear arrangement of a large number of small sources
(e.g. a row of small dome tweeters).
The mechanism may have a rotary mechanism supporting the sound
source. In this case, it is possible for the location repositioning
between the sound source and the acoustic element to be brought
about by twisting the sound source articulated to the rotary
mechanism. In general, however, it is also possible for other
repositioning mechanisms, e.g. unpluggable mounts or the like, to
be provided, and it is also possible for the repositioning to be
achieved not by means of a mechanism which engages with the sound
source but rather by means of a mechanism which engages with the
acoustic element.
Another aspect of the invention relates to a loudspeaker box with a
loudspeaker housing and a sound source which can be positioned in
different rotational positions relative to the loudspeaker housing
a mechanism. In addition; the loudspeaker box comprises a
positioning mechanism for positioning at least one acoustic
element, which dilates or constricts the radiation of sound in at
least one radiation plane, into the sound path of the sound
source.
As already explained, repositioning of the sound source allows the
radiation behaviour of the loudspeaker box to be customized to the
respective application (loudspeaker group or individual solution)
or the respective position of the loudspeaker box (on its side or
upright). However, the acoustic element is required only in one of
these two positions and can be placed in front of the sound source
in this one position by means of the positioning mechanism (e.g.
hinged, swivel or sliding mechanism) or can be retrospectively
fitted on the loudspeaker box in this one position using a
coupling.
The invention is explained below using exemplary embodiments with
reference to the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a perspective illustration of a group of horizontally
oriented loudspeaker boxes;
FIG. 2 shows a perspective illustration of a vertically oriented
loudspeaker box which is suitable for standalone operation;
FIG. 3 shows a perspective illustration of a horizontally oriented
loudspeaker box with an acoustic element, which is suitable for
operation in a loudspeaker group;
FIG. 4 shows a perspective illustration of the vertically oriented
loudspeaker box from FIG. 3 with an acoustic element, which is
reconfigured for standalone operation;
FIG. 5 shows a horizontal sectional illustration along the
sectional line 5-5 in FIG. 3;
FIG. 6 shows a vertical sectional illustration along the sectional
line 6-6 in FIG. 3;
FIG. 7 shows a horizontal sectional illustration along the
sectional line 7-7 in FIG. 4;
FIG. 8 shows a vertical sectional illustration along the sectional
line 8-8 in FIG. 4;
FIG. 9 shows a perspective view of an acoustic lens with a
plurality of perforated panels;
FIG. 10 shows a perspective view of an acoustic lens with a set of
parallel lamellae;
FIG. 11 shows a perspective illustration of a further
reconfigurable loudspeaker box with a positioning mechanism for the
acoustic element; and
FIG. 12 shows a perspective view of a line array.
DETAILED DESCRIPTION
FIG. 1 shows an arrangement comprising three horizontally oriented
loudspeaker boxes 100 situated above one another. Such an
arrangement of loudspeaker boxes 100 occurs in what are known as
line arrays, for example, in which the loudspeaker boxes 100 are
arranged as seamlessly as possible in a vertical column. To expand
the radiation behaviour of the line array in a defined manner and
to provide even sound for the listening area, the loudspeaker
housings 1 of the loudspeaker boxes 100 have a slightly conical
shape so that adjacent loudspeaker boxes 100 can be oriented at a
slight angle with respect to one another in the line array, which
is then somewhat curved.
The text below discusses the lengthwise dimension, the crosswise
dimension and the depth of a loudspeaker housing 1 of a loudspeaker
box 100, the lengthwise dimension being defined as the larger of
the two dimensions appearing in a front view. In FIG. 1, the
lengthwise dimension of the loudspeaker box 100 is thus oriented
horizontally and the crosswise dimension of the loudspeaker box 100
is oriented vertically. The longitudinal direction of the
loudspeaker box 100 may contain a plurality of drivers situated
next to one another, e.g. two outer drivers 2a, 2b and one central
driver (not visible) which opens into a horn 3. The central driver
may be a tweeter driver, for example. The lengthwise dimension may
be more than twice or three times as large as the crosswise
dimension, for example.
In the loudspeaker boxes 100 shown in FIG. 1, the horn 3 has a
diffraction gap 3a which is oriented in a vertical direction. The
effect achieved by this is that the vertical radiation angle of the
tweeter soundwave is relatively small, while the horizontal
radiation angle of the horn 3 can be made much larger. For use in a
line array, provision may be made, by way of example, for the
horizontal radiation angle prescribed by the shape of the horn 3 to
comprise approximately 100.degree., whereas the vertical radiation
angle (likewise prescribed by the shape of the horn 3) of an
individual loudspeaker box 100 comprises only approximately
20.degree.. In a line array application, this vertical radiation
angle of an individual loudspeaker box 100 should not exceed
approximately 25.degree..
FIG. 2 shows a loudspeaker box 200 which is suitable for standalone
operation. In the example shown here, it is oriented upright. The
same or similar parts are provided with the same reference symbols
in the figures. Individually operated loudspeaker boxes 200 are
typically oriented in an upright position. This has partly visual
and acoustic reasons, since in a system with a plurality of drivers
2a, 2b a vertical arrangement generally meets the radiation
requirements (wide horizontally, narrow vertically) better. In this
respect, the loudspeaker box 200 shown in FIG. 2 differs from the
loudspeaker box 100 shown in FIG. 1 in that the diffraction gap 3a
of the horn 3 runs in a lengthwise dimension of the loudspeaker box
200. Furthermore, with a loudspeaker box 200 used as a standalone
solution, the radiation requirements which apply are different from
those for the loudspeaker boxes 100 in a line array which are shown
in FIG. 1. In reference to the tweeter soundwave, it may be
beneficial if a radiation angle of approximately 80.degree. can be
achieved in the horizontal direction. In the vertical direction,
the radiation angle of the tweeter soundwave is supposed to be
larger than the maximum permissible radiation angle for line array
applications, and is supposed to be approximately 40.degree., for
example. The horn 3 of the loudspeaker box 200 for operation as an
individual system therefore needs to be shaped differently from the
horn 3 of the loudspeaker boxes 100 designed for operation in a
loudspeaker group.
The invention is based on the idea that a loudspeaker box (see FIG.
1) provided for a loudspeaker group (e.g. line array) has its
function changed to form a loudspeaker box (see FIG. 2) which is
suitable for standalone operation by repositioning a sound source
with a non-rotationally symmetrical radiation characteristic. Since
repositioning of the sound source particularly in the vertical
direction does not yet provide a usable radiation behaviour
(radiation behaviour is too narrow in the vertical direction), an
acoustic element is also used which corrects the radiation
behaviour in a suitable fashion for the loudspeaker box rotated
through 90.degree.. As discussed in more detail below, it is
likewise possible for the acoustic element instead of the sound
source to be repositioned relative to the loudspeaker box, and for
the acoustic element to be only in one of the positions of the
loudspeaker box in the sound path.
In the exemplary embodiments which follow, the invention is
explained by way of example with reference to a sound source which
is implemented by a diffraction gap 3a (e.g. a horn 3). However,
the loudspeaker boxes according to the invention may also use other
types of sound sources with a non-rotationally symmetrical
radiation characteristic. By way of example, instead of a
diffraction gap 3a, a ribbon tweeter may be provided whose
sound-emitting opening is likewise shaped linearly. A further
option is to use what is known as an air motion transformer (AMT)
as a sound source. AMTs are sound transducers which produce sound
by having a concertinaed diaphragm with conductor tracks arranged
meandrously on it. AMTs are preferably used as tweeters in the
frequency range from approximately 1 kHz to approximately 25 kHz.
By virtue of their design, they likewise have an elongate or linear
sound exit opening. A further option for providing a sound source
having quasi-linear shaping is to provide a linear arrangement of
small loudspeakers (e.g. dome tweeters). All of said sound sources
with linear shaping can optionally be combined with a horn 3, the
shaping of the horn 3 allowing additional shaping of the sound
field emitted by the sound source 3a. It should be pointed out that
in all of the exemplary embodiments which follow, the diffraction
gap 3a serving as a sound source is to be understood merely by way
of example and can be replaced by the aforementioned and other
sound sources with a non-rotationally symmetrical (for example
linear) radiation characteristic, possibly in combination with a
horn 3.
It should also be pointed out that the terms loudspeaker box "on
its side" and "upright" loudspeaker box used here are intended, in
their general meaning, to denote only situations of a loudspeaker
box which are rotated through 90.degree.. Although loudspeaker
boxes in a line array are typically oriented such that their
lengthwise dimension runs in the horizontal direction and their
crosswise dimension runs in the vertical direction, and this is
usually exactly the other way round for loudspeaker boxes which are
suitable for standalone operation, it is also possible to construct
line arrays from loudspeaker boxes with a lengthwise dimension in
the vertical direction and to design boxes which are suitable for
standalone operation to have a lengthwise dimension in the
horizontal direction. The demands to be met on the radiation
characteristics remain unaffected thereby, however, i.e. in this
case too a loudspeaker box in the line array should have a
radiation angle of no greater than approximately 25.degree. in the
vertical, for example.
FIG. 3 shows an exemplary embodiment of a loudspeaker box 300 which
is suitable both for operation in a loudspeaker group and for
operation as an individual box. The loudspeaker housing 1 and the
drivers 2a, 2b correspond to the parts explained in FIGS. 1 and 2
with the same reference symbols. The loudspeaker box 300 differs
from the loudspeaker box 100 shown in FIG. 1 in that the sound path
contains an acoustic element 4 arranged before the horn 3. By way
of example, the acoustic element 4 may be in the form of an
acoustic lens 4. The acoustic lens 4 comprises two lens elements
4a, 4b and causes the radiation angle of the tweeter soundwave to
be dilated in the horizontal direction. By way of example, the horn
3 may be designed such that the radiation angle of the horn 3 is
approximately 80.degree. in the horizontal direction (i.e.
crosswise with respect to the diffraction gap 3a of the horn 3) and
is approximately 20.degree. in the direction of the diffraction gap
3a. The acoustic lens 4 causes this radiation angle to be dilated,
e.g. to approximately 100.degree.. The radiation properties desired
for groups of loudspeaker boxes 100 are thus achieved, see FIG.
1.
FIG. 4 shows the loudspeaker box 300 shown in FIG. 3 in a vertical
arrangement, i.e. oriented upright with the lengthwise dimension in
the vertical direction. The horn 3 with the diffraction gap 3a has
been repositioned through 90.degree. with respect to the position
shown in FIG. 3. The repositioning can be achieved by rotating the
horn 3, for example, which to this end may be attached to a pivot
bearing (not visible). The pivot bearing may be attached to the
tweeter loudspeaker (not shown) or to the loudspeaker housing 1,
for example. If only the diffraction gap 3a or another linear sound
source without a horn 3 is used, the diffraction gap 3a or the
other linear sound source is arranged so as to be appropriately
repositionable or rotatable.
When the horn 3 has been repositioned, it has a radiation angle of
approximately 80.degree. in the horizontal direction and of
approximately 20.degree. in the vertical direction, using the
radiation variables indicated by way of example in FIG. 3. In this
case, the acoustic lens 4, which in this case is fitted on the
loudspeaker housing 1 at a fixed location, for example, influences
only the radiation angle in the vertical direction and dilates it
from 20.degree. (see FIG. 3) to 40.degree.. Hence, a radiation
behaviour is achieved which meets the requirements for a
loudspeaker box which is suitable for standalone operation (see
FIG. 2).
The radiation angle of the horn 3, which is prescribed by the
shaping of the horn 3, in the direction of the diffraction gap 3a
and in the crosswise direction relative to the diffraction gap 3a
and also the change in the radiation angle by the acoustic lens 4
may vary in a wide range according to the field of use and design
of the loudspeaker box 300. This is also possible because the
radiation angles of the horn 3 and the influencing of these
radiation angles by the acoustic element 4 can be attuned to one
another. By way of example, the use of an acoustic lens 4 which
severely dilates the radiation of sound of the horn 3 allows the
use of a horn 3 which has a much smaller radiation angle than
20.degree. in the direction of the diffraction gap 3a. In addition,
as will be explained in more detail below, it is also possible to
use acoustic lenses 4 which constrict the radiation of sound
instead of dilating it, which means that the opposite circumstances
then prevail and, by way of example, it is possible to use a horn 3
whose radiation angle may be much greater than 20.degree. in the
direction defined by the diffraction gap 3a.
If the acoustic lens 4 dilates the radiation of sound, the horn 3
may, in line with one exemplary embodiment, have a radiation
characteristic of no more than 25.degree. in the plane defined by
the diffraction gap 3a. In the position of the loudspeaker box 300
which is shown in FIG. 4, the acoustic lens 4 can then dilate the
radiation characteristic in the plane defined by the diffraction
gap 3a to least 30.degree.. In the plane oriented at right angles
to the diffraction gap 3a, the horn may have a radiation
characteristic of at least 60.degree.. In the position of the
loudspeaker box 300 which is shown in FIG. 3, the acoustic lens 4
can then dilate the radiation characteristic in the plane oriented
at right angles to the diffraction gap 3a to at least 80.degree.,
for example.
FIGS. 5 and 6 show sectional illustrations along the lines 5-5 and
6-6, Respectively, in FIG. 3. On the input side of the horn 3, the
aforementioned tweeter driver 5 is arranged. The tweeter driver 5
and the horn 3 have the aforementioned pivot bearing 7 provided
between them, for example. As can be seen from FIGS. 5 and 6, the
acoustic lens 4 is situated in the sound path downstream of the
exit plane of the horn 3. In the horizontal plane (FIG. 5), the
lens elements 4a, 4b, influencing the soundwave only in sectors to
the side of the main propagation direction (i.e. the central axis
of the horn 3) achieve dilation of the sound field, while in the
vertical direction (FIG. 6) a lens element (in this case 4b)
influences the soundwave evenly over its entire radiation range and
hence does not bring about any change in the radiation angle in the
vertical direction.
FIGS. 7 and 8 show sectional illustrations along the lines 7-7 and
8-8 respectively, in FIG. 4. On account of repositioning of the
horn 3 with the diffraction gap 3a relative to the acoustic lens 4,
opposite circumstances to those in FIGS. 5 and 6 prevail in this
case. The radiation behaviour is not influenced by the acoustic
lens 4 in the horizontal direction (FIG. 7), while in the vertical
direction (FIG. 8) the sound field emitted by the horn 3 is
dilated.
FIGS. 7 and 8 show sectional illustrations along the lines 7-7 and
8-8 respectively, in FIG. 4. On account of repositioning of the
horn 3 with the diffraction gap 3a relative to the acoustic lens 4,
opposite circumstances to those in FIGS. 5 and 6 prevail in this
case. The radiation behaviour is not influenced by the acoustic
lens 4 in the horizontal direction (FIG. 7), while in the vertical
direction (FIG. 8) the sound field emitted by the horn 3 is
dilated.
The acoustic lens 4 can be implemented in a wide variety of ways. A
first implementation option, which has been used by way of example
in FIGS. 3 to 8, involves the acoustic lens 4 being implemented in
the form of perforated panels or perforated sheets. The perforated
panels influence the transmission of the sound. The holes produce a
low-pass filter behaviour which can be set by the hole size and
grid spacing. The low-pass filter causes a change of phase response
and hence a propagation-time behaviour which curves the wavefront.
As FIG. 9 shows, there may also be a plurality of perforated panels
4a1, 4a2 and 4b1, 4b2 arranged above one another, which means that
the sound-field-dilating effect of the acoustic lens 4 is amplified
in the outer region, for example, i.e. for large radiation angles
relative to the central axis of the horn 3.
Another implementation option for the acoustic lens 4 involves
introducing detour elements into the sound field. Detour elements
in the sound field lengthen the path and therefore increase the
propagation time and therefore likewise result in curvature of the
wavefront. An acoustic lens 40 based on the principle of detour
elements is shown by way of example in FIG. 10. The detour elements
used here are parallel lamellae 40a, 40b, 40c, 40d, 40e, 40f, 40g,
40h, 40i which are arranged so as to be inclined with respect to
the central axis z of the horn 3 (the x-y plane is the opening
plane of the horn 3). The longer the detour elements 40a, . . . ,
40i, the more pronounced the propagation-time effect and hence the
effect of the acoustic lens 40. If the lamellae 40a, . . . , 40i
are cut out in a central region 41, i.e. have a shorter length at
that point than in the case of larger radiation angles, the sound
must take a longer detour for larger radiation angles than for
small radiation angles. This results in the sound field being
dilated.
Another option for implementing an acoustic lens 4 is to arrange a
material in front of the horn 3 which alters the speed of sound
locally. A reduction in the speed of sound, e.g. in the regions
shown by the lens elements 4a, 4b in FIGS. 5 to 8, likewise results
in the sound field being dilated.
It is also possible to use acoustic lenses 4 which constrict the
radiation of sound in at least one radiation plane. Such "focusing"
acoustic lenses 4 may be based on the same principles (detour
elements, elements with a low-pass filter behaviour, medium with
different speed of sound). By way of example, one or more
perforated panels in a central region of the horn 3, a detour
element in a central region of the horn 3 or an element with a
reduced speed of sound in the central region of the horn 3 (or
elements which increase the speed of sound in outer regions of the
horn 3) bring about constriction of the radiation of sound.
Another variant involves the acoustic element being designed not as
an acoustic lens operated in transmission but rather as a
reflective body which is implemented at least in part in the sound
path before (i.e. upstream of) the opening plane of the horn 3. In
this case, the acoustic element influences the radiation
characteristic of the horn. By repositioning the acoustic element
relative to the horn 3, it is possible to achieve targeted
alteration of the radiation behaviour of the horn 3 in reference to
the plane defined by the diffraction gap 3a or to said plane's
normal plane.
The acoustic element 4 (lens or reflective body or both) can be
repositioned relative to the horn 3 with a non-symmetrical
radiation behaviour in a wide variety of ways. By way of example,
as already mentioned, the horn 3 may be fitted rotatably on the
tweeter driver 5 or on the loudspeaker housing 1. By way of
example, as indicated in FIGS. 5 to 8, the horn 3 has a round
flange 7 by means of which it is mounted on the tweeter driver 5
and can be rotated through 90.degree.. The horn 3 can be rotated
using, by way of example, a small opening (not shown) on the side
of the loudspeaker housing 1 which allows a hand to access the horn
3. Another option is to attach the horn 3 to the tweeter driver 5
by means of a plug connection, so that unplugging the horn 3 (or
the diffraction gap 3a) allows repositioning through
90.degree..
The acoustic element 4 may be mounted at a fixed location on the
loudspeaker housing 1, provided that the horn 3 (or the diffraction
gap 3a) can be repositioned relative to the loudspeaker housing 1.
Another option is for the acoustic element 4 to be able to be
repositioned relative to the loudspeaker housing 1, e.g. by means
of a plug connection or a rotary mechanism. In this case, the horn
3 (or the diffraction gap 3a) may be arranged at a fixed location
relative to the loudspeaker housing 1. It is also possible for the
horn 3 (or the diffraction gap 3a) and the acoustic element 4 to be
able to be repositioned relative to the loudspeaker housing 1. In
addition, it is also possible for a plurality of different acoustic
elements 4 to be provided, with one acoustic element 4 being
provided for the vertical position of the loudspeaker box 300 and
the other acoustic element 4 being used when the loudspeaker box
300 is positioned on its side.
FIG. 11 shows another exemplary embodiment, which relates to a
loudspeaker box 400 with a loudspeaker housing 1 and a horn 3 (or
diffraction gap 3a) which can be positioned in different rotational
positions relative to the loudspeaker housing 1 using a mechanism.
In addition, the loudspeaker box 400 comprises a positioning
mechanism, for example in the form of a coupling 6, for an acoustic
element which dilates or constricts the radiation of sound from the
horn 3 (or from the diffraction gap 3a) in at least one radiation
plane.
In this exemplary embodiment, as already explained with reference
to FIGS. 3 and 4, the horn 3 (or the diffraction gap 3a) is
repositioned or twisted in order to match the radiation behaviour
of the loudspeaker box 400 in the tweeter range to the respective
situation of use (loudspeaker group or standalone solution) and
position of the loudspeaker box (on its side or upright). However,
the acoustic element 4 is required only in one of these two
situations of use or positions, which is why the loudspeaker box
400 provides the coupling 6 by means of which the acoustic element
4 is fitted on the loudspeaker box 400 in one of the two situations
of use or positions. By way of example, provision may be made for
the horn 3 (or the diffraction gap 3a) to have a radiation
characteristic for which the radiation angle is approximately
100.degree. in the dimension crosswise relative to the diffraction
gap and is approximately 20.degree. in the dimension parallel to
the diffraction gap. In this case, in the position of the
loudspeaker box 400 which is shown in FIG. 3, the desired radiation
angle of approximately 100.degree. in the horizontal direction and
the desired radiation angle of approximately 20.degree. in the
vertical direction, which are suitable for use of the loudspeaker
box 400 in a loudspeaker group (e.g. line array), are achieved. The
loudspeaker box 400 can therefore be operated in a loudspeaker
group without an acoustic element.
When the loudspeaker box 400 is set up in the position shown in
FIG. 11, the horn 3 (or the diffraction gap 3a) is rotated, as
already explained with reference to FIG. 4, so that now a radiation
angle of 100.degree. in the vertical direction and of 20.degree. in
the horizontal direction is produced. Furthermore, an acoustic
element 4 (not shown in FIG. 11) which dilates the radiation of
sound in the vertical direction to 40.degree. is attached to the
loudspeaker box 400 by means of the coupling 6. The acoustic
element 4 may have one of the previously described embodiments and,
by way of example, leave the radiation of sound in a horizontal
direction (which is less critical than the radiation of sound in
the vertical direction) unaffected. Instead of approximately
100.degree., this could also be approximately 80.degree. or an
intermediate angle range for both situations of use (loudspeaker
group and standalone solution). It would also be conceivable to
attach an acoustic element which is a combination of a focusing
element (for the horizontal direction) and a defocusing element
(for the vertical direction), and again all the implementation
forms described above (acoustic transmission lens, acoustic
reflective body) and combinations of these implementation forms may
be used. The coupling 6 fitted on the loudspeaker housing 1, for
example, may be produced in a wide variety of ways, e.g. as a plug
coupling with plug openings 6a, 6b, 6c, 6d onto which an acoustic
element of this kind can be plugged.
If the acoustic element 4 is required only in one of the two
situations of use for the loudspeaker box 400, as illustrated with
reference to FIG. 11, it may also be attached to the loudspeaker
box 400 (e.g. to the loudspeaker housing 1) by means of a swivel,
hinged or sliding mechanism and be swivelled, folded or slid in
front of the horn 3 in the one situation of use, for example. In
this case, instead of the coupling 6, a swivel, hinged or sliding
mechanism (not shown) is provided to which the acoustic element 4
is permanently attached and, as explained, is swivelled, folded or
slid in front of the horn 3 (or the diffraction gap 3a) when
required (e.g. in the configuration suitable for standalone
operation).
In this second exemplary embodiment, the coupling, swivel, hinged
or sliding mechanisms thus form, by way of example, various options
for implementing a positioning mechanism which can be used to put
the acoustic element 4 into the sound path of the sound source
(e.g. diffraction gap 3a, possibly with horn 3) in one situation of
use or position of the loudspeaker box 400 and to remove it from
the sound path of the sound source in the other situation of use or
position of the loudspeaker box 400. Apart from this difference,
the statements made in relation to the first exemplary embodiment
(loudspeaker box 300), in which the acoustic element 4 is arranged
in the sound path of the sound source in both situations of use or
positions of the loudspeaker box 300, also apply to the second
exemplary embodiment illustrated with reference to FIG. 11.
It goes without saying that it is also possible for the sound
source 3a, 3 to be designed such that the loudspeaker box 400 can
be operated in a position (FIG. 4) suitable for standalone
operation without an acoustic element (i.e. the horn 3 has the
desired radiation behaviour of approximately 40.degree. in the
vertical direction and approximately 80.degree. in the horizontal
direction, for example) and the coupling, swivel, hinged or sliding
mechanism which is in the loudspeaker box 400 can be used to put an
acoustic element into the sound path of the sound source 3, 3a,
which acoustic element corrects the radiation characteristic of the
loudspeaker box 400 in the position shown in FIG. 3 to produce the
desired values for use in a loudspeaker group. As already
mentioned, with the loudspeaker groups, the radiation angle in the
vertical direction should be smaller than 25.degree. (e.g.
approximately 20.degree. or possibly even smaller), while the
radiation angle in the horizontal direction can either remain
unchanged (e.g. at approximately 80.degree.) or is optimally above
this and is increased to approximately 100.degree., for
example.
It should be pointed out that the numbers indicated for the
radiation angles may differ substantially from the exemplary
details according to the intended field of use for the loudspeaker
group or for the loudspeaker box 400 which is suitable for
standalone operation.
A common feature of all the exemplary embodiments is that a
loudspeaker box 300, 400 having a sound source 3a with a
non-symmetrical radiation behaviour can be reconfigured from a
loudspeaker box 300, 400 which is suitable for use in loudspeaker
groups to a loudspeaker 300, 400 which is suitable for standalone
operation by simple measures (repositioning the sound source and/or
repositioning an acoustic element 4 and/or adding an acoustic
element 4 and/or swapping two acoustic elements 4).
FIG. 12 shows a line array comprising a plurality of loudspeaker
boxes 300, 400 which are oriented on their side, are linked to one
another and are attached to a fly frame 8. The loudspeaker boxes
300, 400 are connected to one another by means of connecting pieces
13, 14, with variable curvature of the line array being able to be
set on the basis of the conical housing shape.
* * * * *
References